It is known to patrol an array or bank of such spindles by an automatic thread monitor designed to detect the presence of a ruptured filament or loose thread end on any of the spindles. The thread monitor is mounted on a carriage also supporting a yarn-tying or filament-piecing device adapted to connect such a loose end with a fresh oncoming thread. Devices of this type have been described, for example, in U.S. Pat. Nos. 3,128,590 and 3,486,319.
In commonly owned U.S. patent application Ser. No. 875,077, filed by me jointly with Helmut Weiss on Feb. 3, 1978, there has been disclosed and claimed a component of a thread monitor serving to reinsert the loose end of a ruptured filament into the corresponding traveler preparatorily to tying it to a fresh thread. The loose end is picked up by a suction tube and held until a gripper and a coacting deflector can position it in the path of the traveler which is driven around its track by an air stream. The assembly of suction tube, gripper and deflector is supported on a ring rail serving as a common mounting for the track-forming spinning rings of the array, this mounting being vertically reciprocable during the building of the yarn packages to produce successive layers of oppositely slanting turns. A relative axial staggering of these layers, resulting in the formation of tapering extremities or chases on the several yarn packages, is brought about by the superposition of a progressive vertical motion upon the reciprocating traverse of constant stroke imparted to the ring mounting.
As discussed in U.S. Pat. No. 3,641,758, it is desirable to synchronize the operation of a yarn-piecing mechanism--or at least some service unit thereof such as the device for picking up a loose end--with the reciprocation of the ring mounting so as to establish an operating interval for that unit during a certain phase of a traverse, independently of the superimposed progressive shift of the spinning frame carrying the reciprocating ring rail. This operating interval, of course, is utilized only if a thread rupture has been detected at any delivery station serving one of the spindles of the array; the affected spindle is then deactivated and the monitoring carriage is halted in a confronting position to pick up the loose end and to retie it to the fresh thread coming from the associated supply reel or reels. The pick-up device, accordingly, may become operational anywhere along the path of the patrolling carriage.
Thus, the problem arises of correlating the reciprocatory component of the vertical displacement of a ring mounting with the operation of a service unit forming part of a horizontally moving carriage. The solutions heretofore proposed, involving a mechanical linkage between the ring rail and a carriage-supported switch, are relatively complex and correspondingly prone to malfunction.